ISSN 1312-2622

YEAR IX No. 4 / 2011

CONTENTS
An Approach for Equalizing Huge Volume Data Sources with the Network
Volterra Model Predictive Control of Lyophilization Plant: A Newton Optimization Method Approach
Time-dependent Solidification in a Square Cavity with a Temperature-modulated Liquid Layer Cooled from Above
Embedded Robust Control of Self-balancing Two-wheeled Robot
The Satellite Navigation System EGNOS and Safety of Life Service Performance in Sofia

 

An Approach for Equalizing Huge Volume Data Sources with the Network
V. Topalova, R. Raychev
Key Words:
Multimedia data flow; multimedia data archive flow; attr-DB backup flow; network transfer; DBMS.
Abstract:
All well-known techniques for compression could be applied to multimedia data flows transferred via a network. But the transmission of associated with them database archives remains a challenge, because their volume increase on and on in the time. This paper describes a system approach, which manages the transfer of huge, growing in real-time, multimedia archives via the network. The analytical model and clarifying graphics demonstrate significant, over 20 times, diminution of the data volume transffered via the network, compared to the classic transmission practice. This allows reducing both the risk of redundant reservations of network resources and the number of session escapes on timeout. In this way, the sources of huge data volumes could be easier adapted to the network.

Volterra Model Predictive Control of Lyophilization Plant: A Newton Optimization Method Approach
Y. Todorov, S. Ahmed, M. Petrov
Key Words:
Fuzzy-neural models; Newton method; predictive control; lyophilization.
Abstract:
The lyophilization process is widely used by pharmaceutical and food industries preparing stable dried medications and important biopreparations. Recent advances in lyophilization technology impose the application of innovative strategies for reliable determination of the current process conditions and control of the drying cycles. This paper describes a method for designing a nonlinear model predictive controller to be used in a lyophilization plant. The contorller is based on a truncated fuzzy-neural Volterra predictive model and a simplified Newton method as an optimization algorithm. The proposed approach is studied to control the product temperature in a lyophilization plant. Several simulation experiments have been performed in to demonstrate the efficiency of the proposed approach. The obtained results are compared with the classical Gradient optimization procedure.

Time-dependent Solidification in a Square Cavity with a Temperature-modulated Liquid Layer Cooled from Above
S. Kimura, M. Ueda, K. Kanev
Key Words:
Phase change; dynamic solidification; perturbation solution; convection heat transfer; transient phase change; e-learning.
Abstract:
In this work, we investigate the dynamic response of a solid phase formed during unidirectional solidification below a cooling top wall of a square cavity fillied with distilled water and subjected to time-varying heating temperaturesat its bottom wall. Assuming a quasi-steady state condition, we have formulated a one-dimensional model that predicts the average thickness of the forming solid phase. While non-dimensionalizing the model equations, three important non-dimensional parameters are identified, namely the Biot number based on the solid phase thickness at steady state, the Stefan number based on the temperature difference between the cooling upper wall and the liquid temperatures, and the Stefan number based on the heating bottom wall and the liquid temperatures. A perturbation solution of the quasi-steady state formulation has been developed for small amplitude temperature variations on the heating bottom wall. The perturbation solution has been extensively tested against a full two-dimensional numerical solution that uses boundary-tracking techniques for tracing the solid-liquid interface, and good general agreements have been confirmed. The solid phase thickness variation with the time and its phase delays have been expressed as a function of the non-dimensional angular frequence of the heating bottom temperature and the above-mentioned three non-dimensional parameters. The implications of this study and its potential for employment in education and practical engineering have been also addressed.

Embedded Robust Control of Self-balancing Two-wheeled Robot
L. Mollov, P. Petkov
Key Words:
Robust control;embedded systems; two-wheeled robots; µ-synthesis; MATLAB.
Abstract:
This paper presents the design and experimentation of a two degree-of-freedom robust controller for a self-balancinh two-wheeled LEGO Mindstorms NXT robot. A 12-th order discrete-time controller is designed by using the techniques of µ-synthesis. The closed-loop control system achieves robust stability and robust performance in the presence of two uncertain friction coefficient. The experimental results show that the robot preserves stability in the vertical plan for deviations greater than 16.

The Satellite Navigation System EGNOS and Safety of Life Service Performance in Sofia
B. Vassilev, B. Vassileva
Key Words:
Satellite Based Augmentation System; safety parameters.
Abstract:
In this work EGNOS and some syste performance results are presented. The recent system basic parameters performance for Southeast Europe is tested using real data measured by the EGNOS monitoring station placed by Eurocontrol in the Technical University of Sofia. All results are presented in plots showing the achieved performances which are briefly commented in the context of basic KPI of the system.

The John Atanasoff Society of Automatics and Informatics

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